CAGS?????

[Andrew K. Mattei]

>Steve,
>   What is the CAGS solenoid????   That could be it.
>
>Thanks for the hint,
>Dave Hempstead
>

Dave, you strike me as a detail person. Here's "details" from the FAQ at
F-body.org ;)

Hope this helps-

-Andrew

Q: What's CAGS (skip shift) and how does it work?

A: CAGS stands for Computer Assisted Gear Selection and is on 1994 and on
cars with 6 speed transmissions. It's purpose is to improve gas mileage and
avoid the "gas-guzzler" new car tax. CAGS comes into play under the
following conditions:

you're in 1st gear (of course)
you're at 35% throttle or less
you're between 15 and 21 mph
engine coolant temperature is greater than 171 F (77 C)
This will energize the skip-shift solenoid and force a 1st to 4th shift.
What happens is you'll be moving happily along when suddenly the "Skip
Shift" light goes on in the dash. At this point you will be locked out of
2nd and 3rd. You simply cannot shift into them. At this point several
options are available to you:

shift into 4th
shift into 5th
shift into 6th
coast in neutral until the RPMs drop and CAGS is disengaged
>open up the throttle a bit more and shift into 2nd or 3rd
Interestingly, 1st gear is determined by the PCM calculating from the speed
sensor input and the RPM values. Disconnecting the solenoid connector
disables CAGS but an error code 84 WILL be set if the PCM does not measure
voltage at the solenoid connection to the computer for a period of 26 secs.
This code is stored but will NOT light the Service Engine light. Apparently
Chevy correctly anticipated the rush for owners to disable this function. A
resistor inserted in the connector will allow voltage to the PCM input and
prevent this code setting but who cares since the code is reference only.



Q: How do I disable CAGS?

A: There are several electrical connectors going into the transmission.
There are three 2-wire connections on the drivers side of the tranny. Two of
them are hooked up to large, brass colored protrusions which are solenoids.
The third connection is to a small black box on the tailshaft of the tranny.
This is the speed sensor (no speedometer cable on the LT1). Disconnecting
this will stop CAGS, but your speedo will also not work and the check engine
light will come on. Of the other 2 connections, one is up on the tailshaft.
This is the reverse lockout solenoid, although it's really a reverse enable
solenoid since when it is not powered on, you are locked out of reverse. The
final connection is the CAGS solenoid, the farthest forward of the three in
the center of the tranny. Unplug it, tape it, and forget it.

The Service Engine light won't come on if you have a 1994 or 1995 car (note,
no CAGS on the '93s), but the PCM stores an error code of 84 indicating the
open circuit in the CAGS wiring. Since an open circuit (which a disconnected
solenoid would be) using 2 wires can only be detected by no current flow,
simply insert a resistance relatively close to the DC resistance of the
solenoid coil across those wires. That way the current detector will still
see the load, assuming the CAGS solenoid is still there and operational. See
below for instructions on this.



Q: Why does my Service Engine Light come on now that CAGS is disabled?

A: You most likely have 1996 or later car. In 1996, GM instituted the OBD-II
standard on the F-Body computers. This makes modifying the car much more
difficult than in the past. Simple changes (such as disabling CAGS) will
cause the computer to sense a problem and light up the service engine light.
Luckily, you can fool the computer into thinking CAGS is still connected.

The resistance of the CAGS solenoid is 15 ohms. Assuming 13.5 V, that means
about 12 W are dissipated. Go to Radio Shack or any local electronics store
and pick up a 15 ohms, 10 W resistor (about $0.50). 10 W should should be
fine as it will be mounted to the tranny which will work as a heat sink and
the skip shift is only active a few seconds at a time, so there won't be
much time for any extensive heat build up. But in hotter environments, you
might want to use a resistor of 2200 ohms rated at only a 1/4 to 1/2 W.

Simply put the resistor in place of the CAGS solenoid thereby closing the
circuit and making the computer think CAGS is still connected. You can also
buy some heat shrink tubing to put around the resistor to protect it. Then
take a tie wrap and fasten the "eye" of the wire connector to the tranny so
everything is nice and tight. The connection be returned to stock form in
less than 5 minutes if needed and easily be duplicated again for $1.



Q: How do disable the Skip Shift light as well?

A: The following procedure requires a 10mm socket, extension, ratchet, and
awl (or similar tool with a pointed tip):

Disconnect the battery.
Remove the two bolts holding the PCM to the inner fenderwell. (The PCM is
the cigar box sized unit located near the passenger side hood hinge.)
Pull the PCM from its lower retaining slot and position the unit so that the
connectors are accessible.
To disable CAGS, remove the 32-Way F Micro-Pack connector marked "Blue" on
the PCM. There is a red retaining clip that needs to be removed first. (Once
the connector is removed you will be able to see a blue connector pin
guide.)
Use the awl to open the gray connector back shell (3 snap latches).
Use the awl again to remove the blue connector/pin guide located on the
front of the connector (2 snap latches).
Find the white wire in location 15. The pins are marked on the back of the
connector where the wires go in to it.
Gently lift the pin retainer for slot 15 while gently pulling the wire from
the back of the connector. Once the wire end is clear of the retaining
latches, release the pin retainer. Continue to pull the wire until it is
free of the connector body. (There is a seal near the back of the connector
that will add a little resistance to the pulling.)
Tape off the wire end.
Reinstall the connector/pin guide. (It only goes on one way.)
Snap the back shell in place.
Reinstall the connector on the PCM.
Reinstall the PCM by reversing the first two steps.
Reconnect the battery.
Even though the procedure looks complicated and intimidating, it should only
take about 15 minutes to complete. This will cause error code 91 to be set
and stored in the PCM in addition to code 84 set by removing the solenoid.

It is interesting to note that on the pre-OBD-II cars with CAGS (1994-1995),
instead of disconnecting the CAGS solenoid from under the car (as described
in the section above), CAGS can also be disconnected in a similar way to the
shift light disconnection. In addition to removing the connector in location
15 of the "Blue" connection on the PCM, also remove the gray connector at
location 13 of the "Black" connection on the PCM. This will disable CAGS
without having to disconnect anything under the car. However, on the 1996
and later cars, the service engine light will remain lit upon disconnecting
connector 13. So the resistor method as described above is recommended for
those cars.